The present invention relates to drilling machines and, more particularly, to tools for drilling rocks, especially rocks of alternating hardness.
The invention may be most preferably used in the mining industry, preferably at open cut mining for drilling blastholes.
The invention may also be used in the geological practice, in the construction industry and municipal works and other fields where boreholes are to be drilled under complicated geological conditions with non-uniform rock hardness.
At present a problem exists in the drilling technology which is associated with the employment of a single tool for drilling rocks of alternating hardness.
Generally rocks are formed by various alternating layers with a hardness f varying from 1 to 12 by the M. M. Protodyakonov scale, the rocks with a hardness f=1-6 belonging to soft rocks and those with f=6-12 to hard rocks. Interlayers of rocks of various thickness and hardness in depth generally occur without any predetermined regularity. Drilling such rocks by means of conventional machines and bits is associated with certain difficulties and is rather inefficient in a number of applications. All these factors impair technological and economic performance of drilling tools and rigs.
Drilling of complicated rocks with a hardness f=1-12 can be efficient and economically advantageous only in case drilling tools and conditions are adequate for a given type of rock. Rocks with a hardness f=1-6 are preferably drilled with cutting bits and rocks with a hardness f&gt;6 are drilled with cutter-bit and rotary percussive bits. The employment of one type of conventional drilling tools and bits for drilling complicated rocks with f=1-12 or changing tools and bits during borehole drilling depending on hardness of the rock being drilled is economically disadvantageous.